Deputy chief public health officer Dr. Howard Njoo responds to a question during a news conference, Tuesday, Jan. 12, 2021 in Ottawa. THE CANADIAN PRESS/Adrian Wyld

Deputy chief public health officer Dr. Howard Njoo responds to a question during a news conference, Tuesday, Jan. 12, 2021 in Ottawa. THE CANADIAN PRESS/Adrian Wyld

UPDATE: Data suggests Pfizer vaccine may be almost as good after 1 dose as 2

Pfizer to ship nearly three million doses over next six weeks, Moderna more than 1.4 million.

There is compelling evidence that a single dose of COVID-19 vaccines may provide almost as much protection as giving two doses, Canada’s deputy chief public health officer said Thursday.

Dr. Howard Njoo said the advisory committee of federal and provincial public health officers is having an active discussion about whether Canada would be better served to delay the second doses of vaccines in a bid to give protection to more vulnerable people quicker.

“These are what I would call early data in terms of a vaccine effectiveness or studies,” he said. “And the indications are that there’s a good level of protection after just one dose.”

Canada intends to vaccinate three million people with two doses by the end of March.

More than 990,000 Canadians have received at least one dose, and about one-third of those have also received their second doses.

RELATED: Senior homes stay safe as B.C. finds 427 more cases of COVID-19

RELATED: Two young adults from Cowichan Tribes have died of COVID-19

Quebec’s immunization committee went as far Thursday as to recommend nobody get a second dose until a first dose is injected into everyone in six high-risk groups, including people over 70, health-care workers, and people who live in long-term care homes and retirement residences.

The committee reported that single doses have been 80 per cent effective at preventing COVID-19 so far among long-term care residents and health workers who were vaccinated.

Questions about delaying the second doses arose almost as soon as vaccinations began in December, prompting a whirlwind of debate among scientists about the ethics of “going off label.”

Pfizer-BioNTech and Moderna’s vaccines — the two currently authorized in Canada — were tested by giving two doses, 21 days and 28 days apart respectively.

But Dr. Danuta Skowronski, the epidemiology lead for influenza and emerging respiratory pathogens at the British Columbia Centre for Disease Control, said data show two weeks after one dose of either vaccine, the protection against COVID-19 was almost as good as what was found after two doses.

Skowronski and Dr. Dr. Gaston De Serres from the Institut national de santé publique du Québec made the case in a letter published in the New England Journal of Medicine this week.

Moderna reported itself that two weeks after one dose, those who got the vaccine were 92 per cent less likely to develop COVID-19 symptoms.

Pfizer and BioNTech, whose vaccine uses similar genetic technology to Moderna’s, said their vaccine was 52 per cent effective after one dose, but 94.5 per cent effective after two.

Skowronski said Pfizer started measuring illness as soon as the injections were given, which she said is “unreasonable.”

“It’s basic vaccinology that you don’t expect the vaccine to activate the immune system instantaneously,” she said, in an interview with The Canadian Press.

Skowronski said if you wait two weeks to start counting infections, there were 92 per cent fewer infections of COVID-19 among those who got one dose of the vaccine, compared with those who got the placebo.

At that level of protection, she said “we need to get a first dose into our priority populations, and the most vulnerable of those at greatest risk of severe outcomes and the precious resource of our front-line health-care workers.”

She said the second dose should eventually be given but said there isn’t a maximum time she would put on how long to wait.

Pfizer has issued caution about adjusting the dosing schedule but said the decision to do so rests with local authorities.

“We at Pfizer believe that it is critical for health authorities to carry on surveillance on implemented alternative dosing schedules to ensure that vaccines provide the maximum possible protection,” the company’s statement reads.

Canada’s National Advisory Committee on Immunization said in January that the recommended schedule should be followed wherever possible but that delaying a second dose up to six weeks could be beneficial, particularly with a shortage of supplies and a fast-spreading virus.

Skowronski said waiting six weeks instead of three or four for a second dose won’t do much.

“That’s not maximizing coverage that we need to undertake with the scarcity of the vaccine that is available now.”

Several provinces have been delaying the second doses a couple of weeks, particularly as deliveries of both Pfizer-BioNTech’s vaccine and Moderna’s slowed to a crawl in mid-January.

Those delays appear to be over. Pfizer says it will ship nearly three million doses over the next six weeks, and Moderna promises to ship more than 1.4 million.

With the two authorized vaccines, and the two-dose schedule followed, Canada expects to vaccinate 14.5 million people by the end of June and all Canadians who want to be immunized by the end of September.

A new vaccination schedule issued Thursday shows if the other three vaccines currently being reviewed get approved by Health Canada, 24.5 million Canadians could be vaccinated before Canada Day.

Mia Rabson, The Canadian Press

Like us on Facebook and follow us on Twitter.

Want to support local journalism? Make a donation here.

Coronavirus

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

The Terrace & District Chamber of Commerce hosted a virtual all candidates forum for the Coast Mountains School District trustee by-election on Feb. 23, 2021. (Screenshot/Terrace & District Chamber of Commerce Facebook)
Terrace trustee candidates lay out top priorites during virual all candidates forum

All candidates forum was held virtually on Feb. 23, 2021

(Phil McLachlan/Capital News)
Murder charge laid in February 2020 stabbing death of Smithers man

Michael Egenolf is charged with the second-degree murder of Brodie Cumiskey

(Phil McLachlan/Capital News)
Murder charge laid in February 2020 stabbing death of Smithers man

Michael Egenolf is charged with the second-degree murder of Brodie Cumiskey

Island Health chief medical officer Dr. Richard Stanwick receives a first dose of Pfizer vaccine, Dec. 22, 2020. (B.C. government)
COVID-19: B.C. seniors aged 90+ can start to sign up for vaccination on March 8

Long-term care residents protected by shots already given

The Majagaleehl Gali Aks Elementary School in Hazelton is being shut down for a week by the Gitanmaax Band Council following a confirmation of a COVID-19 exposure there on Feb. 26. (Black Press Media File Photo)
COVID-19 exposure notice shuts down Hazelton school

Closure to last for one week and school is to be sanitized

Older rental apartments are prime candidates for renovations, and could result in lost affordable housing stock. (Zoë Ducklow photo)
B.C.’s renoviction overhaul a good start, but won’t preserve affordable stock, lawyer says

And still no protection for people who can’t pay rent due to COVID-19

(Photo by Marissa Baecker/Shoot the Breeze)
B.C. WHL teams to hit the ice with Kelowna, Kamloops hub cities

Kelowna, Kamloops centres chosen to host B.C. WHL teams for 24-game regular season

The machines are akin to ATMs and allow drug users at risk of overdose to get hydromorphone pills dispensed to them after their palm has been scanned to identify its unique vein pattern. (CANADIAN PRESS)
Feds dole out $3.5M for ‘vending machines’ to dispense safer opioids in B.C.

The machines are located in four cities across Canada, including Vancouver and Victoria

Kelowna’s lakefront visitor centre is one of 130 around the province. Tourism businesses have been hardest hit by COVID-19 restrictions on travel. (Destination B.C.)
Tourism, small business getting COVID-19 help, B.C. minister says

$300M grant program has delivered $50 million so far

The incident happened in downtown Castlegar. Photo: Betsy Kline
Castlegar teen recounts stabbing after stranger breaks into grandmother’s house

The unnamed teen survived a terrifying attack Feb. 21

(Black Press file photo)
Agassiz boy, 11, dies from ‘extensive injuries’: Homicide team

Agassiz RCMP were called out Friday to assist with a child in medical distress

Dr. Amit Desai of St. Francis Hospital receives a COVID-19 vaccine on Dec. 17. (Photo courtesy of CHI Franciscan)
B.C. has now vaccinated more people from COVID-19 than total confirmed cases

B.C. has reached a milestone, vaccinating roughly 1.6% of its population from the coronavirus

Most Read